Roger Federer said it was a "special moment" to return to the big stage as he passed a first-round test at the Australian Open on Monday.

The 17-time Grand Slam champion, back in action after a six-month injury layoff, downed his one-time junior rival Jurgen Melzer of Austria 7-5, 3-6, 6-2, 6-2 in just over two hours at Rod Laver Arena.

Roger Federer (SUI) during his first round at the 2017 Australian Open at Melbourne Park in Melbourne, Australia, on Jan 16, 2017. [Photo/IC]

The Swiss 17th seed will now play American qualifier Noah Rubin in the second round.

"It was a special moment walking out on the court. A special moment when you get to match point and when you win it," Federer said of his comeback.

"I think those three components make it special when you're coming back. It's already great to just be here, trying to play with the guys. I'm happy with the more relaxed attitude and also the success came easier."

Federer, 35, is bidding to become the second oldest man in the Open era to win a Grand Slam title, after Australian Ken Rosewall.

Asked about the constant debate about his eventual retirement, Federer said: "It doesn't surprise me because I've been talking about retirement for seven years.

"Naturally that's the perfect opening for people to ask that question yet again, think to themselves, 'Why more?' I get it. It's fine. I'll keep answering it."

Federer, playing in his 69th major, has dropped to 17th in the world rankings after a knee injury restricted him to just seven Tour events last year.

He dropped out of the world's top 10 for the first time in 734 weeks in November and his ranking is at its lowest since May 2001.

Federer fell behind to an early break against Melzer in the opening set but once he gained his playing rhythm he broke back and then again in the 11th game.

Melzer, who grew up in the juniors with Federer, evened the match by taking the second set, but the Swiss legend whipped through the third in 28 minutes with the Australian crowd cheering his every winning point.

Federer finished off in style with two breaks of serve to run a convincing winner.